A lateral access approach is frequently selected to deliver intervertebral fusion cages to the lumbar spine. Compared to conventional anterior or posterior approaches to the lumbar spine, the lateral approach is thought to minimize posterior and/or anterior tissue damage as well as reduce surgery time, associated blood loss, vascular damage and infection risk.
In general, it is known in the art to mount a laterally-placed fusion cage with a plate that secures to the sides of adjacent vertebral bodies. This plate attaches to a side of each vertebral body adjacent the operative disc space. The primary purpose of the plate is to reduce the patient's ability to undergo excessive extension, thereby eliminating the need for the surgeon to implant posterior fixation.
U.S. Pat. No. 7,594,931 (Louis) discloses an intervertebral arthrodesis implant for insertion in an intervertebral space separating opposite faces of two adjacent vertebrae. The implant has a ring-shaped intervertebral cage having a bar that extends perpendicular to the axis of the spine. The bar has a height less than the rest of the cage. A surface of the cage contacting the vertebrae has an undulating shape for limiting sliding of the cage in a plane parallel to the vertebral faces.
PCT Published Patent Application WO2011-080535 (Dinville) discloses anchoring devices, anchoring systems for intervertebral implants, intervertebral implants, and instruments and methods for implanting the implants. In preferred configurations, these various objects share the feature of comprising or cooperating with an anchoring device having a body comprising at least one curved plate elongated along a longitudinal axis. The plate is designed to be inserted through a passage crossing at least a part of the implant in order to penetrate into at least one vertebral endplate and attach this implant onto this vertebral endplate by means of at least one stop retaining the implant. The body of the anchoring device comprises at least one longitudinal rib on at least a part of at least one of its faces, the rib being designed to cooperate with a groove made in a passage of implant.
In one type of intervertebral device suited for the lateral approach, the fusion cage is mounted with a plate that secures the cage to the adjacent vertebral bodies. In particular, US Published Patent Application 2010-0004747 (Lin) discloses a spinal fixation device comprising a trans-vertebral and intra-vertebral plate and a rectangular cage with a slot for the plate for neutralizing intervertebral movement in spinal interbody fusion. The rectangular cage with a vertical or oblique slot is inserted into the intervertebral space from the lateral or anterior side of the spinal column. The plate is then inserted through the slot of the cage and hammered into and buried inside the two adjacent vertebral bodies to achieve three-dimensional intervertebral fixation.
U.S. Pat. No. 6,432,106 (Fraser I) discloses a spinal fixation assembly includes a fusion cage to which a plate is mated. The plate is configured to receive, retain and orient bone screws.
U.S. Pat. No. 7,112,222 (Fraser II) discloses one type of prior art device that combines a cage with a plate, so that the cage is integrally bound to the plate. A representative side view of this assembly is shown in FIG. 14.
U.S. Pat. No. 7,112,222 (Fraser II) further discloses a spinal fixation assembly is provided including a fusion cage with posterior, anterior, superior, and inferior faces, and a plate having at least one aperture for receiving a bone screw and having a mating element adapted to slidably engage and mate to the anterior face of the fusion cage. The cage is adapted to be positioned between adjacent vertebrae, and the plate is effective to mate to the cage and to receive one or more bone screws to fasten the plate and secure the fusion cage to the adjacent vertebrae.
US Published Patent Application US 2011-0184415 discloses (Anderson) discloses a bone stabilization system is provided having a plate with a top and bottom surface and a hole therethrough extending along a longitudinal axis. An annular groove in the top surface encircles the axis and defines outer facing sides of a plurality of spring members integral to the plate. A plurality of slots define sides of the spring members the inward facing side of the spring members form the upper portion of the hole, which includes a first spherical portion. A fastener with a spherical portion on the fastener head extends into the hole with the spring members urged apart to allow the head to pass but restraining removal until the resistance provide by the spring members is overcome.
US Published Patent Application US 2007-0049941 discloses (Thramann) discloses a spinal fusion plate includes a means to support an adjacent vertebral segment to inhibit the adjacent vertebral segment from further degeneration. The means to support includes an attachment to an associated artificial disc or nucleus replacement, an extension, or an attachment to a bone anchor. In each case, the attachment is moveable in relation to the fusion plate to allow flexion and extension.
U.S. Pat. No. 7,887,595 (Pimenta) discloses a spinal fusion implant of non-bone construction to be introduced into an intervertebral disc space for the promotion of spinal fusion.